Cruciate replacing artificial knee

ABSTRACT

A prosthetic knee with an artificial ACL/PCL. The prosthetic knee includes a femoral component and a tibial component. The artificial ACL/PCL connects the femoral component and the tibial component and includes an anterior cruciate ligament portion connecting an anterior anchor point on the tibial component to a posterior anchor point on the femoral component, and a posterior cruciate ligament portion connecting a posterior anchor point on the tibial component to an anterior anchor point on the femoral component. The artificial ligament may be provided as single length of material and may be pre-assembled into an ACL/PCL module having portions that may be inserted into at least one of the femoral component or the tibial component. A system is also provided for total knee replacement that includes a selection of femoral components, tibial components, and one or more ACL/PCL modules of varying sizes.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of PCT International Application No.PCT/US2015/062386, filed Nov. 24, 2015 claiming the benefit of U.S.Provisional Application No. 62/084,017 filed on Nov. 25, 2014, thecontents of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

This invention relates generally to artificial knee prostheses used forTotal Knee Replacement (TKR), and more particularly, to a knee jointprosthesis having a more anatomically accurate artificial anteriorcruciate ligament (ACL) and/or posterior cruciate ligament (PCL).

BACKGROUND OF THE INVENTION

Prosthetic knees generally include three main components, a femoralcomponent (FIGS. 1A and 1B), which is attached to the distal end of thefemur, a tibial component (FIGS. 2A and 2B), which is implanted onto theproximal end of the tibia, and an articular insert (FIGS. 3A and 3B),which is mounted onto the tibial component and provides a frictionalsurface for the femoral component. The components are designed tosimulate a joint and the associated mechanics of a human knee throughoutthe knee's range of motion. The components are generally provided in avariety of shapes with varying dimensions (identified as dimensions A-Hand J-T in FIGS. 1A to 3B), so that a physician is able to select theoptimal combination of components depending on the specific anatomy ofthe patient. The size and shape of the knee is dependent on variousfactors including age, gender, and size of the patient. Therefore, afairly large inventory of components are generally made available, sothat the prosthetic knee may be tailored for the patient,

During the course of a routine knee construction with a TKR, the ACL isremoved in a vast majority of all cases and depending on the selectedTKR design, the patient's PCL is either retained or substituted withsome mechanism to replace the lost function of the PCL. Even when thePCL is retained, often a portion of the PCL must be cut or partially cutduring surgery to aid in the balancing of the knee replacement. When thePCL is completely removed, the PCL is substituted by a post and cammechanism.

Referring to FIGS. 1A, 1B, 3A, and 3B, an illustration of a typicaldesign of a post and cam mechanism is provided. An articular insert 22includes an extension 24 that protrudes into an opening 12 of thefemoral component 10. The extension 24 includes a posterior surface 25that is intended to be in frictional contact with the posterior surface14 of the opening 12 when the joint is flexed. The resistance generatedwhen the extension 24 bears against the posterior surface 14 of theopening 12 in the femoral component 10 is intended to simulate theresistance that would have been generated by a healthy posteriorcruciate ligament (PCL). Cam and post mechanisms have been manufacturedthat partially replace the function of an ACL by creating a cam surfacebetween the anterior surface of the extension 24 and the anteriorsurface of the opening 12; however, this solution provides only apartial substitution of an ACL because the anterior side of theextension 24 is at best able to contact the anterior side of the openingonly between 0 to 20 degrees of flexion.

Another solution is to connect the femoral component and tibialcomponent with a cable-like material, such as the material disclosed inU.S. Pat. No. 5,935,133, the contents of which are incorporated hereinby reference. But this artificial material is typically only used toreplace the PCL and not the ACL.

These common solutions are deficient in that a replacement has not beenprovided to generate resistance simulating an ACL. Essentially, the ACLis sacrificed. The lack of an anatomically correct replacement mayresult in a TKR having reduced functionality compared to the originalknee. This may create difficulties during physical therapy followingsurgery, as well as limit the patient's ability or desire to participatein physical activity following therapy. Virtually all modern total kneereplacements sacrifice the ACL or inadequately substitute it with acrude cam and post mechanism, thus leaving the reconstructed knee withkinematics similar to that of an ACL-deficient knee. Normal kneekinematics therefore remain elusive. In addition, the lack of properinterplay between an ACL and PCL (which together drive normal kneekinematics) leaves the TKR reconstruction short of producing arelatively normal knee for the patient.

Given the complexity of the mechanics of a knee joint and the difficultyfor patients to adjust to an artificial knee after surgery, ananatomically correct knee replacement system is needed that moreaccurately simulates the resilience and support formerly provided by theremoved ligaments.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a prosthetic knee isprovided that comprises a femoral component, a tibial component, and atleast one artificial ligament connecting the femoral component and thetibial component, the at least one artificial ligament comprising ananterior cruciate ligament portion connecting an anterior anchor pointon the tibial component to a posterior anchor point on the femoralcomponent, and a posterior cruciate ligament portion connecting aposterior anchor point on the tibial component to an anterior anchorpoint on the femoral component. The tibial component comprises anarticular insert configured to be coupled to the tibial component andthe at least one artificial ligament comprises a single length ofmaterial in which the anterior cruciate ligament portion and theposterior cruciate ligament are connected to one another. In anotherembodiment, the anterior cruciate ligament portion and the posteriorcruciate ligament portion may be discrete components that are notconnected to one another.

In another embodiment of the present invention, an ACL/PCL module isprovided. The module may be attachable to a prosthetic knee having afemoral component, an articular insert, and a tibial component and maycomprise at least one of a femoral portion configured to be coupled tothe femoral component and a tibial portion configured to be coupled toat least one of the articular insert and the tibial component and atleast one artificial ligament connecting the femoral component and thetibial component. The at least one artificial ligament comprises ananterior cruciate ligament portion connecting an anterior anchor pointon the tibial portion or tibial component to a posterior anchor point onthe femoral portion or femoral component, and a posterior cruciateligament portion connecting a posterior anchor point on the tibialportion or tibial component to an anterior anchor point on the femoralportion or femoral component. The at least one artificial ligament maycomprise a single length of material in which the anterior cruciateligament portion and the posterior cruciate ligament are connected toone another, or the anterior cruciate ligament portion and the posteriorcruciate ligament portion may be discrete components that are notconnected to one another.

In yet another embodiment of the present invention, a system forproviding total knee replacement on a plurality of patients of differentsizes is provided. The system may comprise a plurality of femoralcomponents, a plurality of tibial components, a plurality of articularinserts, and at least one ACL/PCL module. The plurality of femoralcomponents comprise a plurality of differently sized femoral componentseach configured to accommodate a range of patient femoral anatomies. Theplurality of tibial components comprise a plurality of differently sizedtibial components each configured to accommodate range of patient tibialanatomies. Each articular insert is configured for installation betweenthe distal portion of the femur on which one of the plurality of femoralcomponents is fixed and the proximal portion of the tibia on which oneof the plurality of tibial components is fixed. The ACL/PCL modulecomprises at least one of a femoral portion configured to be coupled toone or more of the femoral components and a tibial portion configured tobe coupled to one or more of the tibial components or one or more of thearticular inserts, and at least one artificial ligament connecting thefemoral component and the tibial component. The at least one artificialligament comprising an anterior cruciate ligament portion connecting ananterior anchor point on the tibial portion or the tibial component to aposterior anchor point on the femoral portion or the femoral component,and a posterior cruciate ligament portion connecting a posterior anchorpoint on the tibial portion or tibial component to an anterior anchorpoint on the femoral portion or the femoral component.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a side view of a femoral component for a knee jointprosthesis known by those of ordinary skill in the art;

FIG. 1B is a bottom view of the femoral component of FIG. 1A;

FIG. 2A is a top view of a tibial component for a knee joint prosthesisknown by those of ordinary skill in the art;

FIG. 2B is a side view of the tibial component of FIG. 2A;

FIG. 3A is a top view of an articular insert for a knee joint prosthesisknown by those of ordinary skill in the art;

FIG. 3B is a front view of the articular insert of FIG. 3B mounted onthe baseplate of a tibial component;

FIG. 4 is a side view of a knee joint illustrating the anatomicallocation of the ACL and PCL and the configuration of an artificialmaterial intended to replace the ACL and PCL according to one embodimentof the present invention;

FIG. 5 is a side view of a femoral component, articular insert, andartificial ligament for a TKR according to another embodiment of thepresent invention;

FIG. 6A is a top view of a cross-section along line I-I of FIG. 5;

FIG. 6B is a bottom view of a cross-section along line I-I of FIG. 5;

FIG. 7A is a top perspective view of an ACL/PCL module of an embodimentof the present invention;

FIG. 7B is a top perspective view of an ACL/PCL module of anotherembodiment of the present invention;

FIG. 7C is a top perspective view of an ACL/PCL module of yet anotherembodiment of the present invention;

FIG. 8 is a top perspective view of the femoral portion of theembodiment illustrated in FIG. 7A with a femoral component;

FIG. 9A is a top perspective view of a tibial portion according toanother embodiment of the present invention;

FIG. 9B is a top view of an articular insert that may be combined withthe tibial portion of FIG. 9A;

FIG. 10A is a top view of a tibial portion according to yet anotherembodiment of the present invention;

FIG. 10B is a side view of the tibial portion of FIG. 10A; and

FIG. 10C is an articular insert that may be combined with the tibialportion of FIG. 10A.

DETAILED DESCRIPTION

In order to provide a more anatomically correct TKR, prosthesisembodiments that replicate the function provided by both the ACL and PCLare desirable. Referring to FIG. 4, a healthy human knee is illustratedwith a loop 30, representing an exemplary artificial ACL/PCL ligament,drawn over the location of the original anatomical ACL and PCL. Thesection of the loop 30 constituting the artificial PCL is bounded bypoints 26A and 26B. The section of the loop 30 constituting theartificial ACL is bounded by points 28A and 28B.

Generally, the present invention provides various methods of utilizingan artificial material, preferably a synthetic fiber or cord, to replacean ACL and PCL, such that the artificial material is configuredsimilarly to the respective orientation and location of the ACL and PCLin a normal knee. It should be understood, however, that the term“artificial” means only that it is not the original anatomical ACL orPCL ligament in its original form prior to the TKR, and should not beinterpreted as a limitation to the use of only synthetic materials.Accordingly, the artificial ligament, may comprise “natural” materials,such as materials fashioned from biologically created materials and/ormay comprise a hybrid of synthetic and natural materials. Specifically,the configuration is such that the origin and insertion points of theartificial material in a TKR is similar to the origin and insertionpoints of the ACL and PCL in a normal knee.

For example, according to various embodiments of the present invention,the artificial material in the form, for example, of artificial ligamentmay be incorporated into the TKR either at the time of surgery or theTKR may be pre-assembled with the artificial material in advance ofsurgery. At the time of the surgical procedure, the surgeon may useeither a single strand of artificial ligament that is woven between thefemoral component and articular insert with attachment points on eitherthe femoral component or the articular insert of the TKR, or the surgeonmay use two lengths of artificial material, one for the ACL and theother for the PCL. Alternatively, the TKR may be preassembled in asimilar fashion in advance of surgery.

Once the artificial material is in place, metallic pieces may be used tocrimp and permanently grip the ends. These metal pieces, however thenpreferably lock into the appropriate anatomical end points of an ACL andPCL in a manner such that the ends of the artificial material do notmove or fret. Alternatively the ends of the artificial material may bebrought in proximity of one another and tied or sewn together into acontinuous loop. In another embodiment, smooth round metal balls may beused to crimp the artificial material and anchor the ends of theartificial material into the articular insert. The round shape of theballs allows the artificial material to move very slightly, reducingstress at the attachment point. Using a spherical anchor that has adiameter larger than the diameter of the artificial material and thediameter of the exit hole in the articular insert may also reduceimpingement and stress at these points. It is preferable to include asmooth tunnel in the articular insert, tibial component, and/or femoralcomponent through which the artificial material may be inserted, withthe ends of the tunnel located in the approximately correct anatomicallocation of the endpoints of the ACL and PCL in the knee. Preferably,the opening of each side of the tunnel is also smooth. A smooth tunnelmay protect the artificial material from the bone and prevent otherpotential problems, such as impingement and fretting of the artificialmaterial during movement of the TKR.

In one method according to the present invention, the artificialmaterial, such as an artificial ligament, may be provided separatelyfrom the TKR. During the replacement procedure, the surgeon may weavethe ligament through the femoral component and articular insert andfasten the ends. Care should be taken when using this method in order tolimit the potential error that may result, for example, from inadequatefastening or leaving an inappropriate length of artificial ligament whenfastening is completed.

In another embodiment of the present invention, a single strand ofartificial ligament may be weaved through a channel in the femoralcomponent of a TKR and the ends of the artificial ligament may beattached to a tibial insert that locks into the tibial baseplate. Thearticular insert may then be provided with cut-outs to allow passage ofthe artificial ligament to the femoral component from the tibial insert.The femoral component of the TKR of this embodiment may be pre-assembledwith the artificial ligament and the tibial insert. The tibial insertmay be standardized to fit into any size tibial component of a TKR.However, the length of the artificial ligament may be variable toaccommodate different size femoral components and articular inserts.

Alternatively, the artificial material may be attached to the articularinsert, such that the articular insert, artificial material, and thefemoral component are pre-assembled together. During the TKR after thefemoral component and the tibial component are in place, the articularinsert may be snapped onto the tibial component in typical fashion.However, because articular inserts and femoral components are providedin different sizes, multiple combinations of the femoral components andarticular inserts may result in a large inventory of differentpre-assemblies.

In yet another embodiment, one or more artificial ligaments may be woventhrough and/or the ends anchored to one or more modular inserts. Themodular inserts may be inserted into one or more of the femoralcomponent, tibial component, and articular insert of the TKR.

Referring now to FIGS. 5, 6A, and 6B illustrating a first embodiment ofthe present invention, the connection points 26 a, 26 b, 28 a, and 28 bof the artificial material, provided as ligament 44, and the lengthsspanning between the connection points, provided as an outline of theartificial ligament 44, are configured to simulate the dimensions andattachment points of the ACL and PCL in a human knee, as illustrated inFIG. 4. At least one length of artificial ligament, such as for examplethe material disclosed in U.S. Pat. No. 5,935,133, may be provided toconnect the articular insert and femoral component of a TKR. Theligaments may be strung during surgery and fastened.

In a preferred embodiment, the artificial ligaments comprise a cord-likematerial. Preferred ligament materials are non-elastic or minimallyelastic, similar to a natural ligament. Exemplary materials may comprisea variant of a woven polyethylene similar to material previouslymarketed as SecureStrand® cable, a braided, ultra high molecular weightpolyethylene (UHMWPE) cable used for surgical fixation in posteriorspinal reconstruction, material currently marketed as Super Cables®(Kinamed, Inc., Camarillo, Calif.) made from UHMWPE and Nylon 6/6,6,Gore-tex® (PTFE fiber manufactured by W. L. Gore and Associates, Inc.Newark, Del.), carbon fiber, or other similar woven materials.

In one embodiment, the artificial ligament 44 comprises a single lengthof material that weaves between the femoral component 34 and articularinsert 32. For example referring to FIGS. 5, 6A, and 6B, a single lengthof artificial ligament may extend from a first end disposed adjacent anupper inner surface of femoral component 34 at an attachment point 26 bin the femoral component 34 to and through the top surface of thearticular insert 32 through opening 26 a, The underside of the articularinsert 32 may have a groove (not shown) or a bore within the thicknessof the insert 32 to define a path between openings 26 a and 28 a toreceive ligament 44, which then extends from the underside of articularinsert 32 through opening 28 a to an attachment point 28 b in thefemoral component 34, such that the second end of the ligament 44 isalso disposed on the upper inner surface of the femoral component. Theends of the artificial ligament 44 may be fastened to the femoralcomponent using any fastening means known in the art, such as but notlimited to a clip or a knot. Alternatively, each end of the artificialligament 30 may define a loop, and the fastening means may include ahook on a surface of the femoral component 34 or one or more fasteners,such as a screw or nail inserted through the loops and into the femoralor tibial component. Alternatively, the ends of the artificial ligamentmay be connected to each other to form a continuous loop.

The location of the ends and the order in which artificial ligament 44weaves among points 26 a, 26 b, 28 a, and 28 b is not limited to anyparticular configuration, as long as the ACL/PCL structure creates atleast one connection between openings 26 a and 26 b and at least oneconnection between openings 28 a and 28 b, as illustrated in FIG. 4. Forexample rather than starting at either attachment point 26 b or 28 b inthe femoral component 34, as illustrated in FIG. 5, the starting andending points may be 26 a or 28 a in the articular insert. The use of asingle strand in various embodiments of the present invention ispreferable because it reduces the number of parts needed to fabricatethe artificial ACL/PCL of the TKR; however, two or more lengths of theartificial ligament 44 may also be used.

Referring again to FIGS. 1A to 3B, it is common for manufacturers toprovide knee prostheses of varying sizes and shapes in order toaccommodate different patients, For example the dimensions of thefemoral component 10, tibial component 16, and articular insert 22labeled as A to H and J to T may vary with respect to a plurality ofsizes to accommodate variations in human anatomy. For example, aparticular TKR system design may feature a plurality of standard sizetibial components (e.g. 10, for a Journey® Knee by Smith & Nephew), aplurality of standard size femoral components (e.g. 10, for a Journey®Knee by Smith & Nephew), and a plurality of standard size articularinserts (e.g. 4, for a Journey® Knee by Smith & Nephew), forming a vastnumber of acceptable combinations and permutations. The physician beforeand during surgery typically measures and selects the correct sizecomponents to include in the TKR, based upon the size of the individualreceiving the TKR and their relevant bone and joint structures.Therefore, in some embodiments, artificial ligament 44 may not be placedbetween the femoral component and the articular insert until after thecorrect size components have been selected.

Knee replacement surgery requires the use of anesthetics. In order toensure patient safety, doctors strive to perform the TKR procedure asquickly and efficiently as possible. During the procedure, the positionof the various components of the prosthetic knee joint may bemanipulated on the femur and tibia until the final position is set.Accordingly, it may be preferable to avoid connecting the femoralcomponent and articular insert with an artificial ligament until closeto the end of the procedure, when the components are in place on thepatient. Because it may be difficult to weave the artificial ligamentbetween the femoral component and the articular insert after thecomponents have been installed, another embodiment of the presentinvention provides a removable ACL/PCL module that is separate from thefemoral component and articular insert. The ACL/PCL module may bepre-assembled and may house the artificial ligaments, such that when thefemoral component and tibial component of a TKR are in place, theACL/PCL module may then be easily inserted and fastened between the twocomponents.

An ACL/PCL module according to various embodiments of the presentinvention are illustrated in FIGS. 7A-10C. The module 36 includes atleast one of an upper femoral portion 40 and a lower tibial portion 42connected by an artificial ligament 44. The artificial ligament 44 maybe one or more strands, preferably a single strand woven between the twoportions. For example, the artificial ligament 44 may have an end 37Bthat is fastened to one upper inner side of the upper femoral portion40. The artificial ligament 44 may then extend from one side of thefemoral portion 40, through the posterior part of the tibial portion 42(substituting for the PCL), from the posterior to the anterior along theundersurface of the tibial portion 42, through the anterior of thetibial portion 42 (substituting for the ACL), and then fastened toanother upper inner surface of the femoral portion 40 at end 37A. Theresulting upper femoral portion 40 and lower tibial portion 42 thereforeare attached to form one linked piece, for example, by one band. Otherconfigurations for connecting artificial ligaments between the femoraland tibial portions of the module may also be used. For example,multiple artificial ligaments, such as segments 44 a and 44 b in FIG.7B, may be used to connect the respective parts of the module ratherthan a single ligament or the starting and ending positions may differfor a single ligament configuration.

The locking mechanism for the ends of the artificial ligaments are notlimited to any particular construction. For example, in the embodimentillustrated in FIG. 7B, the ends of ligament sections 44 a, 44 b withinthe tibial portion 42 are anchored with a spherical retainer 38. Thespherical retainer 38 preferably has a diameter which is larger than theopening in the tibial portion 42 through which the ligament sections 44a, 44 b are inserted. The retainer may be applied to the ends of theligament sections 44 a, 44 b by any methods known to those of skill inthe art. For example, the spherical retainer 38 may be crimped onto theends of the ligament sections 44 a, 44 b. Another example of a lockingmechanism is illustrated at end 37 a of ligament section 44 a, The end37 a is attached to the femoral portion 40 by inserting the end 37 athrough a loop 39 attached to the upper inner surface femoral portion40. The another type of retainer 47, such as a metal clip having a widthgreater than the inner dimension of the loop 39, may be attached to theend 37 a to maintain the ligament section 44 a within the loop 39.Alternatively, the retainer 47 may be used to join the two upper ends ofthe ligament sections 44 a, 44 b. As previously mentioned, the mechanismmay also be provided in the form of a hook 48, as illustrated in FIG.7C, and the retainer 47 may instead be used to form a loop in the end 37a of the ligament section 44 a. The ligament loop may then be secured tothe hook 48. Alternatively, loops present on one or both ends of theartificial ligament may be fastened to one or both of the femoralportion and tibial portion of the ACL/PCL module with a fastener, suchas a nail or screw. For example, a fastener 49 in the form of a nailillustrated in FIG. 7C is inserted through loops at the ends of theartificial ligament 44 in the tibial portion 42 of the module. As wouldbe understood by one of skill in the art, the ACL/PCL modules accordingto the present invention may utilize different combinations of fasteningmechanisms and are not limited to the combinations illustrated in FIGS.7A-7C.

The upper and lower portions of the ACL/PCL module may be made of thesame or similar material as the femoral component, tibial component,and/or articular insert, or a different material. In general, however,all materials are preferably inert, not prone to cause infection, andotherwise safe and approved for use as a surgical implant. Exemplarymaterials include polyethylene, surgically approved metal alloys,surgically approved ceramic materials, or a combination thereof. Anywell-known materials in the field of surgical implants may be used tofabricate any of the various embodiments or portions thereof accordingto the present invention.

One aspect of the exemplary embodiment comprising both an artificial ACLand PCL in a modular construction, is that the module may be easily andremovably secured to the femoral component of a TKR. As illustrated inFIG. 8, a gap 54 may be provided in the femoral component 50 betweenmedial 52A and lateral 526 portions intended to replicate the medial andlateral condyle and the intercondylar fossa of the femur. The width ofthe gap 54 may be substantially equal to the width 43 of the upperfemoral portion 40 of the ACL/PCL module, to permit the attendingphysician to slide the module into place, such that the side walls 41Aand 416 frictionally engage the medial and lateral portions 52A and 526of the femoral component 50.

In another aspect of this exemplary embodiment, lower tibial portion 42may be easily and removably inserted into an articular insert 60. Thetop surface 62 of the articular insert 60 may include a groove 61. Thesides 64A, 646 of the groove 61 may optionally converge to provide ataper. The bottom tibial portion 42 of the ACL/PCL module may have sidewalls 45A, 456 with optional recesses 46 a, 46 b that mate with sides 64a, 64 b of groove 61. Side walls 45 a, 45 b of the bottom tibial portion42 may be parallel or converge to a lesser degree than the sides 64 a,64 b of the groove 61 to secure the bottom tibial portion 42 to thearticular insert 60 in a self-locking taper configuration, such as whatis commonly referred to as a Morse taper. Instead of providing thegroove 61 in the articular insert 60, the groove 61 may alternatively beprovided in the top surface of an tibial component of a TKR, such as thetibial component 16 in FIGS. 2A and 2B; however, an articular insertused with such a modified tibial component comprises a correspondingcutout, for example, such as the articular insert 72 of FIG. 10Cdescribed in more detail below. The ligament 44 attached, embedded,and/or inserted in the tibial portion 42 illustrated in FIG. 9A may bedirectly connected to a femoral component of a TKR or to a femoralportion of an ACL/PCL module, such as the femoral portion 40 illustratedin FIG. 7B.

A particularly preferred embodiment of the present invention isillustrated in FIGS. 10A-10C. In the embodiment of FIGS. 10A-10C, theartificial ligament 44 is embedded, attached, and/or inserted in araised platform section 78 of a tibial baseplate 76. A fastener 74 mayextend from the bottom surface of the tibial baseplate 76. The fastener74 may be attached to a rod, such as a typical rod 18 associated with atibial component of a TKR, as illustrated in FIG. 2B. Any means known tothose of skill in the art may be used to fasten the tibial portion 76 toa rod. For example, the fastener 74 may be in the form of a screw withcorresponding threads provided in the rod or a Morse taper may be usedto combine the components. This embodiment therefore allows for theselection of various rod lengths (identified as dimension N in FIG. 2B).

In order to insert an articular insert between the tibial portion 76illustrated in FIGS. 10A and 10B and the femoral component of a TKR, thearticular insert 72 may be provided with a cutout 80, as illustrated inFIG. 10C. The cutout 80 may have the same or a similar shape as theraised platform section 78. The cutout 80 therefore allows the articularinsert 72 to be inserted from the anterior side of the tibial baseplate76 after the artificial ligaments have been secured. The ligaments 44attached, embedded, and/or inserted in the raised platform section 78may be directly connected to a femoral component of a TKR or to afemoral portion of an ACL/PCL module, such as the femoral portion 40illustrated in FIG. 7B.

The shape, size, and orientation of the upper and lower portions of theACL/PCL module is not limited. For example both the upper and lowerportion may be shaped like the lower portion 42 illustrated in FIG. 9Aand the femoral component 50 may be provided with a groove similar togroove 61 of the articular insert 60. Such a construction may simplifymanufacturing by reducing the number of different components. In anotherembodiment, rather than have a two-piece tibial baseplate, the lowerportion may be a one-piece design, such as in the form of an articularinsert similar to the embodiment illustrated in FIG. 5, with a differentanchoring feature that allows attachment of the artificial ligaments tothe lower portion. Preferably, in this embodiment, two artificialligaments connect the standard articular insert and the modular femoralportion together, such that the attending physician may slide the entireinsert into place during the surgical procedure. In another iteration,the artificial ligament may be anchored in the articular insert at oneend, extend through a tunnel in the femoral component (not shown),return through the tibial component to an anchor at the other end. Thetype of fastening mechanism used to attach each portion of the module tothe femoral component and articular insert or tibial component may alsoinclude any of one or more means known in the art for attachment. Forexample, the femoral portion of the module may use a Morse taper, ascrew-in fastener, or both. Any combination and order of connecting thecord-like material between the two parts of the module may beacceptable, as long the result is a TKR having an artificial ACL andPCL.

The use of an ACL/PCL module in various embodiments of the presentinvention is preferable because not only does the module allow theindividualized selection of a femoral component, tibial component, andarticular insert for a patient who will undergo a TKR procedure, but italso provides a standard ACL/PCL module that may be used with anycombination of components. For example, all of the femoral componentsmade and sold by a manufacturer may include the same size gap 54illustrated in FIG. 8 to accommodate a standard size femoral portion 40of an ACL/PCL module, regardless of the other dimensions of the femoralcomponent, for example dimensions A,B, and D-H in FIGS. 1A and 1B. Therelative distance between the top of the tibial component and the bottomof the femoral component of the prosthetic knee is generally constant;therefore, the ligaments may have a constant length, regardless of theother dimensions of the components. Therefore, only a minor modificationto an existing product line may be needed to incorporate an ACL/PCLmodule according to the present invention, and only a single or alimited number of modules may be provided to accommodate all of thevarious acceptable combinations and permutations of existing components.While it may be particularly advantageous to have only a single modularcomponent size, it may be found that providing multiple sizes providesadvantages, so the modular embodiment is not limited to only a singlesize embodiment.

While preferred embodiments of the invention have been shown anddescribed herein, it will be understood that such embodiments areprovided by way of example only. Numerous variations, changes, andsubstitutions may occur to those skilled in the art without departingfrom the spirit of the invention. Accordingly, it is intended that theappended claims cover all such variations that fail within the spiritand scope of the invention.

I claim:
 1. A prosthetic knee comprising: a femoral component configuredfor fixation to the distal portion of a femur; a tibial componentconfigured for fixation to the proximal portion of a tibia, the tibialcomponent comprising an articular insert configured to be coupled to thetibial component, and an artificial ligament connecting the femoralcomponent and the tibial component, the artificial ligament comprisingan anterior cruciate ligament portion connecting an anterior anchorpoint on the tibial component to a posterior anchor point on the femoralcomponent, and a posterior cruciate ligament portion connecting aposterior anchor point on the tibial component to an anterior anchorpoint on the femoral component, wherein the artificial ligamentcomprises a single continuous length of material in which the anteriorcruciate ligament portion and the posterior cruciate ligament areconnected to one another.
 2. The prosthetic knee of claim 1 furthercomprising an ACL/PCL module attachable to the prosthetic knee, saidACL/PCL module comprising: at least one of a femoral portion configuredto be coupled to the femoral component and a tibial portion configuredto be coupled to at least one of the articular insert and the tibialcomponent; and the artificial ligament connecting the femoral componentand the tibial component.
 3. The prosthetic knee of claim 2, wherein thetibial portion comprises an insert configured to be releasably coupledto the articular insert.
 4. The prosthetic knee of claim 2, wherein thetibial portion comprises an insert configured to be releasably coupledto the tibial component.
 5. The prosthetic knee of claim 2, wherein thefemoral portion comprises an insert configured to be releasably coupledto the femoral component.
 6. The prosthetic knee of claim 2, whereineach end of the single length of material is fastened to the tibialportion.
 7. The prosthetic knee of claim 2, wherein each end of thesingle length of material is fastened to the femoral portion.
 8. Theprosthetic knee of claim 2, wherein the ends of the single length ofmaterial are attached to one another to form a continuous loop.
 9. Theprosthetic knee of claim 2, wherein the femoral portion of the module isconfigured to slidably engage the femoral component or the tibialportion of the module is configured to slidably engage the tibialcomponent.
 10. The prosthetic knee of claim 2, wherein the module isconfigured to be retained in engagement with the femoral component via alocking taper or retained in engagement with the tibial component via alocking taper.
 11. The ACL/PCL module of claim 2, wherein the artificialligament comprises at least one of polyethylene, carbon fiber, and PTFE.12. The prosthetic knee of claim 1, wherein each end of the singlelength of material is fastened to the tibial component.
 13. Theprosthetic knee of claim 1, wherein each end of the single length ofmaterial is fastened to the femoral component.
 14. The prosthetic kneeof claim 1, wherein the artificial ligament comprises at least one ofpolyethylene, carbon fiber, and PTFE.
 15. The prosthetic knee of claim1, wherein the artificial ligament passes through a tunnel, bore orgroove formed in the tibial component, and each end of the single lengthof material is fastened to the femoral component.